A few years ago I saw somebody play a prank on somebody by associating the .exe file extension with Internet Explorer. This made Internet Explorer open up every time the person wanted to start a program.

Unfortunately, I forgot how this was done. I tried to use the Default Programs > Set Associations Control Panel tool, but it didn't list .exe.

How could one set this file association, and, perhaps more importantly, how could one unset it?

2 Answers
2

When doing "pranks" like that, it is not enough to just follow a step-by-step tutorial or a batch script; it's best to know something about how the actual data is stored – it becomes easier to recover later.

All file associations are kept in Registry, which can be edited using regedit or reg. The shell looks for them under HKEY_CLASSES_ROOT, which is a merged view of HKEY_LOCAL_MACHINE\Software\Classes (system-wide) and HKEY_CURRENT_USER\Software\Classes (user-local).

For most extensions, the HKCR\.extn\(Default) value points to a file type key under the same HKCR; for example, .exe points to HKCR\exefile.

(In rare cases, though, all information is under the extension's key directly, with HKCR\.extn\(Default) containing the description. These seem to be very rare, though – maybe a leftover of Windows 9x or 3.x...)

Make backups. reg save HKLM\Software\Classes hklm-classes.hiv Also, remember that the Command Prompt does not care about extensions; if you try to run an executable program, it will always run no matter how it is named, or what its extension is associated with.